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Key Features

Essentials of Diagnosis

  • Pain and effusion of the knee

  • Pain along the lateral joint line

  • Positive Lachman test

General Considerations

  • The anterior cruciate ligament (ACL) consists of two bundles that prevent anterior subluxation and rotation of the tibia

  • Most ACL injuries are noncontact and occur with deceleration, twisting, and cutting motions

  • ACL injuries can also occur with knee hyperextension or from a direct blow to the knee—typically on the lateral side—which causes an extreme valgus stress with both ACL and MCL disruption

Clinical Findings

  • The athlete often reports hearing or feeling a "pop" followed by swelling that occurs within hours of the injury

  • Evaluation of the knee begins with examination of the uninjured knee


  • The Lachman test

    • Provides the most accurate information about knee stability in relation to the ACL

    • Perform by holding the knee in 30 degrees of flexion while supporting the tibia and femur

    • Proximal tibia is pulled anteriorly, and the degree of excursion and the firmness of the endpoint are assessed and compared to the contralateral side

    • All other structures of the knee should be examined to rule out concomitant injuries

  • Imaging of the knee includes plain radiographs and an MRI scan

  • In skeletally immature athletes, a tibial spine avulsion is frequently seen on radiographs rather than a midsubstance ACL tear


  • Initial treatment focuses on controlling swelling and pain

  • Conservative treatment

    • Includes bracing, strengthening, and restricting physical activity

    • Can be complicated by continued instability and damage to meniscal and articular cartilage

  • Surgical reconstruction

    • Typically indicated for young athletes in cutting sports and is also required for persistent instability

    • Can be performed 2–6 weeks following the injury if the swelling and motion of the knee have improved

    • Recent advances in surgical treatment of the skeletally immature athlete have been helpful in dealing with the complicated management of young athletes with ACL tears

  • Rehabilitation of the knee

    • Starts immediately after surgery

    • Goals of a structured physical therapy: building strength, muscle reeducation, endurance, agility, and coordination



  • Return to sport can be achieved by 6 to 9 months after surgery if certain criteria are met


Schub  D, Saluan  P: Anterior cruciate ligament injuries in the young athlete: evaluation and treatment. Sports Med Arthrosc Rev 2011;19:34–43
[PubMed: 21293236] .

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